Staphylococcus epidermidis (S. epidermidis) is a species of staphylococcal bacteria that are Gram-positive, nonmotile, nonpigmented and coagulase-negative cocci, which are mainly found on the skin and mucous membrane of warm-blooded animals. Their large numbers and ubiquitous distribution result in frequent contamination of specimens collected from or through the skin, making these organisms amongst the most frequently isolated in the clinical laboratory. In the past, S. epidermidis was rarely the cause of significant infections, but with the increasing use of implanted catheters and prosthetic devices, it has emerged as an important agent of hospital-acquired infections and has been recognized as a true pathogen (Lowy and Hammer, 1983, Ann Intern Med. 99: 834–9; Blum and Rodvold, 1987, Clin Pharm, 6: 464–75; Hamory, Parisi et al., 1987, Am J Infect Control, 15: 59–74). S. epidermidis is a major cause of infection of indwelling foreign devices such as, orthopedic devices, intravenous catheters, prosthetic heart valves, central nervous system shunts, and peritoneal dialysis catheters (Blum and Rodvold, 1987, Clin Pharm, 6: 464–75; Archer, 1988, J Antimicrob Chemother, 21 Suppl C: 133–8)(Lowy and Hammer, 1983, Ann Intern Med, 99: 834–9; Hamory, Parisi et al., Staphylococcus 1987, Am J Infect Control, 15: 59–74). In addition S. epidermidis is a common cause of postoperative wound infections, bacteremia of immunosuppressed patients, intensive-care unit patients and premature newborns (MacLowry, 1983, Am J Med, 75: 2–6)(Eykyn, 1988, Lancet, 1: 100–4). According to a national survey (Centers for Disease Control, 1981:7) S. epidermidis caused 8.9% of primary nosocomial bacteremias.
Treatment of S. epidermidis infections remains difficult because of the occult nature, association with foreign bodies, and frequent resistance to antimicrobial agents. Ordinarily, S. epidermidis is an organism with low virulence, however breaks in host defense caused by surgery, catheter placement, prosthesis insertion or immuno-suppression is prerequisite for infection. The presence of foreign bodies itself facilitates infection by protecting the organism from elimination by host defenses or antimicrobial therapy (Lowy and Hammer, 1983, Ann Intern Med, 99: 834–9). Furthermore, S. epidermidis due to its ability to produce extracellular polysaccharide material or slime, may be uniquely adapted to adhere to smooth surfaces such as plastics or metal. Slime producing strains of S. epidermidis appear to be more pathogenic than non-slime producing strains (Christensen, Simpson et al., 1983, Infect Immun, 40: 407–10; Peters and Pulverer, 1984, J Antimicrob Chemother, 14 Suppl D: 67–71; Gallimore, Gagnon et al., 1991, J Infect Dis, 164: 1220–3). This property and many factors are involved in the pathogenesis of device associated infections. Despite the increased recognition as a pathogen, S. epidermidis infections are difficult to diagnose. Differentiating clinically important from clinically unimportant bacterial isolates of S. epidermidis is difficult because of the high rate of contamination.
Although laboratory isolates of S. epidermidis have generally been susceptible to semisynthetic penicillins (methicillin, nafcillin, oxacillin), cephalosporins, amino-glycosides, vancomycin and rafampin, recent clinical isolates have had an increased resistance. Recent reports (Karchmer, 1985, Am J Med, 78: 116–27; Karchmer, 1991, J Hosp Infect, 18 Suppl A: 355–66) show that 83% of S. epidermidis isolates from patients with prosthetic valve endocarditis are methicillin resistant and 32% are gentamicin resistant as well. Multi-drug resistant staphylococci have emerged in the midst of high level use of penicillin and aminoglycosides (Centers for Disease Control and Prevention, 1993 MMWR 42:597; and S. Handwerger et al., 1993, Clin Infect Dis 16:750).
The use of antibiotics for therapeutics and prophylactic purposes, promotes the selection of resistant organisms and the spread of antibiotic resistance genes among bacteria. Previous studies have shown that virtually all staphylococci carry some antibiotic resistance genes on naturally occurring extrachromosomal mobile genetic elements, such as the plasmids. Survey and analysis of plasmids in clinical isolates of S. epidermidis have shown that more that 80% of isolates carry plasmids and in several cases more than one plasmid (Archer et al., 1982, Infect Immun, 35:627–632; Kloos et al., 1981, Can J Microbiol, 27:271–278; Moller, 1988, J Hosp Infect 12:19–27). Though the most important forms of resistance has been the inactivation of antibiotics, particularly penicillins and cephalosporins, recent clinical isolates have resistance to one or more of the following antibiotics, methicillin, tetracycline, erythromycin, gentamycin, kanamycin and chloramphenicol. In fact due to the wide spread occurrence of plasmids and their involvement in antibiotic resistance, plasmid profiling has been used as an epidemiological reagent to study nosocomial infections. This invention relates to isolated nucleic acids and polypeptides derived from S. epidermidis plasmids that are useful as molecular targets for diagnosis, prophylaxis and treatment of pathological conditions, as well as materials and methods for the diagnosis, prevention, and amelioration of pathological conditions resulting from bacterial infection.
These concerns point to the need for diagnostic tools and therapeutics aimed at proper identification of strain and eradication of virulence. The design of vaccines that will limit the spread of infection and halt transfer of resistance factors is very desirable.